With the rising cost of petroleum, alternative sources of gasoline or other liquid fuels will be important to addressing transportation fuel issues in the future. The US has abundant coal resources and many people are considering biomass and other carbon sources for conversion to alternative fuels. Generally, these carbon based materials are converted to synthesis gas or syngas (hydrogen and carbon monoxide) which are synthesized into hydrocarbons. A commonly known process is the Fischer-Tropsch synthesis process practiced by the Germans during World War II. Fischer-Tropsch has numerous limitations including a bias to the production of linear paraffins which have very low octane.
Syngas conversion to methanol and/or dimethyl ether (DME) has been discussed and considered and while there are merits, the essentially non-existent infrastructure and markets are a significant barrier to their adoption as transportation fuels, per se. Creating new ways to make existing fuels, such as gasoline, are the technologies that are most likely to be successful. For example, the conversion of DME to gasoline is known, but has a significant production of isomers of durenes (tetramethyl benzenes). Durene (1,2,4,5 tetramethyl benzene) requires additional processing to isodurene (1,2,3,5 tetramethyl benzene) or less substituted aromatics and may reduce the gasoline yield. Also, DME conversion to gasoline tends to produce gasoline that has excessive amounts of benzene which is carcinogenic and only very small amounts are permitted in saleable gasoline.
U.S. Pat. No. 6,066,770, U.S. Pat. No. 6,395,949 and U.S. Pat. No. 6,417,421 teaches the ability to utilize zeolites to produce hydrocarbons however they do not teach a starting material that has oxygenated feed. These patents utilize low carbon number alkane and aromatic hydrocarbons such as butane, pentane, hexane, benzene, toluene and xylenes to produce gasoline with corresponding low carbon numbers. These patents do not teach to the ability to utilize oxygenated feeds to produce gasoline with low durene levels.
New technologies or improvements to existing technologies are highly desirable for any fuels, and especially transportation fuels.